Most installers overrate the available wind resource. The majority of small wind turbine installations underperforms their predictions, often by a wide margin. Since wind speed is the most important parameter for turbine energy production, getting that wrong has large consequences (the power in the wind goes with the cube of the wind speed, so double the wind speed and the power in it is 2 * 2 * 2 = 8x as much). You have to be realistic about your annual average wind speed.
Most small wind turbines do not perform quite as well as their manufacturers want you to believe. That should come as no surprise at this point. What may be surprising is that even the turbines of the more honourable manufacturers that are honest about performance fall short, more often than not. The likely cause is turbulence and improper site selection.
Geothermal power is cost effective, reliable, sustainable, and environmentally friendly, but has historically been limited to areas near tectonic plate boundaries. Recent technological advances have expanded the range and size of viable resources, especially for applications such as home heating, opening a potential for widespread exploitation. Geothermal wells release greenhouse gases trapped deep within the earth, but these emissions are much lower per energy unit than those of fossil fuels. As a result, geothermal power has the potential to help mitigate global warming if widely deployed in place of fossil fuels.
Solar power is the conversion of energy from sunlight into electricity, either directly using photovoltaics (PV), indirectly using concentrated solar power, or a combination. Concentrated solar power systems use lenses or mirrors and tracking systems to focus a large area of sunlight into a small beam. Photovoltaic cells convert light into an electric current using the photovoltaic effect.